usage of chalk
What is its main use? Are there other uses?
How does chalk work?
Chalk is very powdery so how it works is that when one rubs it against chalkboard, it gets off the stick of chalk and comes on to the board. Then, it stays on the board because water is added to it during the manufacturing process. Similarly, chalk also stays on sidewalks and in cave walls. But when you rub it with foam, or a cloth, the powder comes off the board or the sidewalk.